1. Field of the Invention:
This invention relates to refrigeration chambers, and more particularly to means for preventing moisture condensation within the insulation material in the wall structures of said chambers.
2. Description of the Prior Art:
Air movement through the insulated walls of a refrigeration building or chamber is a well-recognized phenomenon and is considered to be due to the fact that cold air, having a greater density than warm air, sinks to the bottom of the chamber, resulting in a higher pressure at the lower portion than the outside air pressure. At the top of the chamber, the pressure is less than the outside air pressure. Accordingly, air tends to flow through the insulated walls and ceiling into the chamber at the upper portion and flow outward at the lower portion. Inward flow of warm ambient air is harmful in that moisture condenses within walls and causes deterioration of insulation and wall structure.
A number of proposals by others have been made to eliminate this problem. Illustrative are the U.S. Pat. Nos. 1,947,223 to Ophuls; 2,151,713 to Niemann; 2,244,005 to Gustin, Jr., et al,; and 2,485,630 to Munters.
It has been proposed by Ophuls, U.S. Pat. No. 1,947,223 to avoid these problems by maintaining the pressure within the entire refrigerated building somewhat higher than the external pressure, whereby cold air would flow outwardly through the walls. He also suggests a false wall around the entire insulating wall structure with a space therebetween and maintaining a subatmospheric pressure in the intermediate space. This solution involves extensive structural additions with attendant increases in cost. Additionally, inwardly swinging doors would be difficult to open against the increased air pressure, and considerable refrigerated air would rush out each time a door is opened. Replacement air would have to be refrigerated.
Nieman--U.S. Pat. No. 2,151,713 cools atmospheric air and injects the cooled air into the interior insulation of the refrigerator walls.
Gustin, Jr., et al.--U.S. Pat. No. 2,244,005 provides a ventilation system for the insulation.
Munters--U.S. Pat. No. 2,485,630 shows passing cold dried air through the insulation.
None of these patents employs the simple means of this invention to solve this vexatious problem.
In De Vries U.S. Pat. No. 3,965,698, which is hereby incorporated by reference, the crawl space above the ceiling of a refrigerated building is maintained at a negative pressure, whereby the flow of ambient air into the upper part of the said building is prevented. While effective, this may entail costly structural changes to create the necessary space for the negative air pressure system.
In contrast to the above, in this invention the upper wall region and ceiling are pressurized by a relatively simple means of local effectiveness so that no excessive amount of cold air escapes on opening the door, and no excessive air pressure renders opening an inwardly swinging door difficult.